Optical instruments such as cameras and/or video cameras have been so commonly used in daily life that variations of them have been widely incorporated into portable electronic devices such as smart phones, tablet computers, as well as mobile surveillance units such as digital image and/or video recorders for home use or installed in vehicles or in buildings. Very often, these optical instruments or their variations comprise one or more light transmissible optical components such as optical lenses, and, during their manufacturing process, inspection of these optical lenses for defects has always been challenging. Lens inspection generally requires specialized skills of the human inspector, and the process can be highly time consuming and labor intensive. Existing methods of inspection may involve manual and visual checking for defects at the lens such as black spots, scratches, white dots, dust or dirt particles, air bubbles, digs, smudges, flow marks and/or other injection or coating defects, but not all of these defects are readily identifiable through visual checking alone. Quality of such inspections is thus largely dependent on the judgement and experience of the inspecting individual, which could be subjective and inconsistent. Accuracy of the inspections may further be compromised, especially during a mass production process, where a large number of lenses are to be manually and visually inspected quickly. It would be understandable that continuous and repetitive visual checking for long hours may cause vision fatigue or even damage to one's eyesight, which may further deteriorate quality and reliability of the inspection process.
US2004/0100629 discloses a method for altering the phase and/or amplitude of an optical beam within an inspection system using one or more spatial light modulator(s) (SLMs). The apparatus includes a beam generator for directing an incident optical beam onto a sample whereby at least a first portion of the incident optical beam is directed from the sample as an output beam and a detector positioned to receive at least a portion of the output beam. The sample being inspected comprises any of a reticle, photomask, printed circuit board or silicon wafer or device. A target image of the sample derived from the output beam is compared to a reference image to determine if any parts of the target image differ by more than a predetermined threshold amount from a corresponding part of the reference image to thereby identify defects. This method requires a reference image for comparison to identify defects in a target image, but the production of suitable reference images can lead to the identification of false defects in target images.
There is a need for an improved apparatus and method for inspecting light transmissible optical components such as optical lenses to identify defects in said optical components.